Kidneys Inc.

medicine and nephrology updates and interesting cases by a practicing nephrologist in USA

Archive for the month “May, 2011”

Lactic acidosis in metformin overdose

Lactic acidosis associated due to metformin is rare and especially so in normal renal function. I had the opportunity to see this. 45 y old woman with major depression who had been prescribed metformin but had not been taking it, ingested about 90 tablets as a suicidal attempt. Seen in the ER within 2-3 hours after ingestion, given charcoal, started on gentle IV hydration, admitted for monitoring. Lactate was elevated to 5.1. Renal function was completely normal with Creatinine of 0.9. Lactate decreased to 0.9 within 24 hours.

Metformin decreases lactate metabolism by suppressing pyruvate carboxylase in the Kreb’s cycle. Glucose utilisation is decreased and lactate production by the hepatocytes is increased.

Bile salts and hypokalemia

Last week, I saw a 53 y old man admitted with end stage liver disease due to chronic alcoholism. He was admitted for altered mental status, acute kidney injury with rise in creatinine from 0.8 about two months ago to 3.4 at the time of admission. However, his serum potassium was 2.4 with transtubular potassium gradient (TTKG ) of 13 (indicates renal wasting). His total bilirubin was 32.

Bile acids are known to cause this low aldosterone and salt retentive states by inhibiting 11 beta hydroxy steroid dehydrogenase enzyme. This enzyme normally converts cortisol into cortisone. When inhibited, as in the above example, it allows normal cortisol to drive sodium absorption and renal potassium wasting in the distal tubules.

Embryology of human kidneys

I intended to post an article on embryology of the kidney. This article just made it easier.

Pronephros draining from the coelom into the pronephric ducts (approximately day 22 of gestation)

Mesonephros draining directly from capillaries into mesonephric (wolffian) ducts: this system is similar to that of aquatic amphibians and fish

Metanephros draining from capillaries into bowman’s capsules and renal tubules (approximatesly by 5th week) and then into metnephric duct that later forms ureters.

While the metanephric ducts travel caudally to join the bladder as ureters, the metanephri rotate and migrate upwards as the torso elongates during development of fetus. this elongates the ureters.

At the end of formation of fully functional kidneys which is by 32- 36 weeks, there are one million nephrons.

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